The present invention relates generally to semiconductor fabrication and, more particularly, to a method for monitoring a semiconductor wafer during a spin drying operation, a method for spin drying a semiconductor wafer, and an apparatus for spin drying a semiconductor wafer.
In the fabrication of semiconductor devices, a variety of wafer preparation operations are performed. In conventional wafer cleaning systems, the wafers are scrubbed in a brush station, which typically includes a first brush box and a second brush box. A wafer is first scrubbed in the first brush box in a solution containing specified chemicals and deionized (DI) water. After being moved into the second brush box, the wafer is again scrubbed in a solution containing specified chemicals and DI water. The wafer is then moved into a spin, rinse, and dry (SRD) station where DI water is sprayed onto the top and bottom surfaces of the wafer as the wafer is spun. Once the wafer has been thoroughly rinsed, a spin drying operation is performed to dry the top and bottom surfaces of the wafer.
The spin drying operation must thoroughly dry the top and bottom surfaces of the wafer. If the spin drying operation is stopped prematurely, i.e., before the surfaces of the wafer are thoroughly dry, then the fluid remaining on the surfaces of the wafer may adversely affect subsequent fabrication operations. On the other hand, if the spin drying operation lasts longer than necessary to dry the surfaces of the wafer thoroughly, then the throughput productivity of the wafer cleaning system suffers. In conventional wafer cleaning systems, spin drying operations are not monitored to determine precisely when the surfaces of the wafer are thoroughly dry. Consequently, these wafer cleaning systems run the risk of either stopping the spin drying operation prematurely or unnecessarily extending the length of the spin drying operation.
In view of the foregoing, there is a need for a method for determining precisely when the surfaces of the wafer are thoroughly dry in a spin drying operation. In addition, there is a need for a method and apparatus for spin drying a semiconductor wafer that enables the spin drying operation to be stopped precisely when the surfaces of the wafer are thoroughly dry.